Re: [PATCH vhost 3/7] vdpa/mlx5: Allow modifying multiple vq fields in one modify command

Eugenio Perez Martin
2023-12-01T14:48:02Z

On Fri, Dec 1, 2023 at 11:49 AM Dragos Tatulea <dtatulea@nvidia.com> wrote:
>
> Add a bitmask variable that tracks hw vq field changes that
> are supposed to be modified on next hw vq change command.
>
> This will be useful to set multiple vq fields when resuming the vq.
>
> The state needs to remain as a parameter as it doesn't make sense to
> make it part of the vq struct: fw_state is updated only after a
> successful command.
>

I don't get this paragraph, "modified_fields" is a member of
"mlx5_vdpa_virtqueue". Am I missing something?

> Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
> ---
> drivers/vdpa/mlx5/net/mlx5_vnet.c | 48 +++++++++++++++++++++++++------
> 1 file changed, 40 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index 12ac3397f39b..d06285e46fe2 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -120,6 +120,9 @@ struct mlx5_vdpa_virtqueue {
> u16 avail_idx;
> u16 used_idx;
> int fw_state;
> +
> + u64 modified_fields;
> +
> struct msi_map map;
>
> /* keep last in the struct */
> @@ -1181,7 +1184,19 @@ static bool is_valid_state_change(int oldstate, int newstate)
> }
> }
>
> -static int modify_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *mvq, int state)
> +static bool modifiable_virtqueue_fields(struct mlx5_vdpa_virtqueue *mvq)
> +{
> + /* Only state is always modifiable */
> + if (mvq->modified_fields & ~MLX5_VIRTQ_MODIFY_MASK_STATE)
> + return mvq->fw_state == MLX5_VIRTIO_NET_Q_OBJECT_STATE_INIT ||
> + mvq->fw_state == MLX5_VIRTIO_NET_Q_OBJECT_STATE_SUSPEND;
> +
> + return true;
> +}
> +
> +static int modify_virtqueue(struct mlx5_vdpa_net *ndev,
> + struct mlx5_vdpa_virtqueue *mvq,
> + int state)
> {
> int inlen = MLX5_ST_SZ_BYTES(modify_virtio_net_q_in);
> u32 out[MLX5_ST_SZ_DW(modify_virtio_net_q_out)] = {};
> @@ -1193,6 +1208,9 @@ static int modify_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtque
> if (mvq->fw_state == MLX5_VIRTIO_NET_Q_OBJECT_NONE)
> return 0;
>
> + if (!modifiable_virtqueue_fields(mvq))
> + return -EINVAL;
> +

I'm ok with this change, but since modified_fields is (or will be) a
bitmap tracking changes to state, addresses, mkey, etc, doesn't have
more sense to check it like:

if (modified_fields & 1<<change_1_flag)
// perform change 1
if (modified_fields & 1<<change_2_flag)
// perform change 2
if (modified_fields & 1<<change_3_flag)
// perform change 13
---

Instead of:
if (!modified_fields)
return

if (modified_fields & 1<<change_1_flag)
// perform change 1
if (modified_fields & 1<<change_2_flag)
// perform change 2

// perform change 3, no checking, as it is the only possible value of
modified_fields
---

Or am I missing something?

The rest looks good to me.

> if (!is_valid_state_change(mvq->fw_state, state))
> return -EINVAL;
>
> @@ -1208,17 +1226,28 @@ static int modify_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtque
> MLX5_SET(general_obj_in_cmd_hdr, cmd_hdr, uid, ndev->mvdev.res.uid);
>
> obj_context = MLX5_ADDR_OF(modify_virtio_net_q_in, in, obj_context);
> - MLX5_SET64(virtio_net_q_object, obj_context, modify_field_select,
> - MLX5_VIRTQ_MODIFY_MASK_STATE);
> - MLX5_SET(virtio_net_q_object, obj_context, state, state);
> + if (mvq->modified_fields & MLX5_VIRTQ_MODIFY_MASK_STATE)
> + MLX5_SET(virtio_net_q_object, obj_context, state, state);
> +
> + MLX5_SET64(virtio_net_q_object, obj_context, modify_field_select, mvq->modified_fields);
> err = mlx5_cmd_exec(ndev->mvdev.mdev, in, inlen, out, sizeof(out));
> kfree(in);
> if (!err)
> mvq->fw_state = state;
>
> + mvq->modified_fields = 0;
> +
> return err;
> }
>
> +static int modify_virtqueue_state(struct mlx5_vdpa_net *ndev,
> + struct mlx5_vdpa_virtqueue *mvq,
> + unsigned int state)
> +{
> + mvq->modified_fields |= MLX5_VIRTQ_MODIFY_MASK_STATE;
> + return modify_virtqueue(ndev, mvq, state);
> +}
> +
> static int counter_set_alloc(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *mvq)
> {
> u32 in[MLX5_ST_SZ_DW(create_virtio_q_counters_in)] = {};
> @@ -1347,7 +1376,7 @@ static int setup_vq(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *mvq)
> goto err_vq;
>
> if (mvq->ready) {
> - err = modify_virtqueue(ndev, mvq, MLX5_VIRTIO_NET_Q_OBJECT_STATE_RDY);
> + err = modify_virtqueue_state(ndev, mvq, MLX5_VIRTIO_NET_Q_OBJECT_STATE_RDY);
> if (err) {
> mlx5_vdpa_warn(&ndev->mvdev, "failed to modify to ready vq idx %d(%d)\n",
> idx, err);
> @@ -1382,7 +1411,7 @@ static void suspend_vq(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *m
> if (mvq->fw_state != MLX5_VIRTIO_NET_Q_OBJECT_STATE_RDY)
> return;
>
> - if (modify_virtqueue(ndev, mvq, MLX5_VIRTIO_NET_Q_OBJECT_STATE_SUSPEND))
> + if (modify_virtqueue_state(ndev, mvq, MLX5_VIRTIO_NET_Q_OBJECT_STATE_SUSPEND))
> mlx5_vdpa_warn(&ndev->mvdev, "modify to suspend failed\n");
>
> if (query_virtqueue(ndev, mvq, &attr)) {
> @@ -1407,6 +1436,7 @@ static void teardown_vq(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *
> return;
>
> suspend_vq(ndev, mvq);
> + mvq->modified_fields = 0;
> destroy_virtqueue(ndev, mvq);
> dealloc_vector(ndev, mvq);
> counter_set_dealloc(ndev, mvq);
> @@ -2207,7 +2237,7 @@ static void mlx5_vdpa_set_vq_ready(struct vdpa_device *vdev, u16 idx, bool ready
> if (!ready) {
> suspend_vq(ndev, mvq);
> } else {
> - err = modify_virtqueue(ndev, mvq, MLX5_VIRTIO_NET_Q_OBJECT_STATE_RDY);
> + err = modify_virtqueue_state(ndev, mvq, MLX5_VIRTIO_NET_Q_OBJECT_STATE_RDY);
> if (err) {
> mlx5_vdpa_warn(mvdev, "modify VQ %d to ready failed (%d)\n", idx, err);
> ready = false;
> @@ -2804,8 +2834,10 @@ static void clear_vqs_ready(struct mlx5_vdpa_net *ndev)
> {
> int i;
>
> - for (i = 0; i < ndev->mvdev.max_vqs; i++)
> + for (i = 0; i < ndev->mvdev.max_vqs; i++) {
> ndev->vqs[i].ready = false;
> + ndev->vqs[i].modified_fields = 0;
> + }
>
> ndev->mvdev.cvq.ready = false;
> }
> --
> 2.42.0
>